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Math Help - bayes theorem disease problem

  1. #1
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    bayes theorem disease problem

    A=event that the tested person has the disease
    B= event that the test is positive
    we know P(B/A)=.9 AND P(B/not A)=0.1
    also 1% of population hs the disease
    find p(A/B)


    i know you use bayes formula here but I dont know how you get the value of p(A) to put in the formula!!the formula im using is [p(B/A)P(A)]/[P(B/A)P(A)+P(B/NOTA)P(NOTA)

    I think I hae all values but p(a) and is the 1% of population used in answer??

    got .0833 as an answer i used .01 as p(a)
    Last edited by mr fantastic; November 22nd 2010 at 10:41 AM. Reason: Merged posts.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by eleahy View Post
    A=event that the tested person has the disease
    B= event that the test is positive
    we know P(B/A)=.9 AND P(B/not A)=0.1
    also 1% of population hs the disease
    find p(A/B)


    i know you use bayes formula here but I dont know how you get the value of p(A) to put in the formula!!the formula im using is [p(B/A)P(A)]/[P(B/A)P(A)+P(B/NOTA)P(NOTA)

    I think I hae all values but p(a) and is the 1% of population used in answer??
    yes


    got .0833 as an answer i used .01 as p(a)
    OK

    CB
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